چکیده انگلیسی

This study examined the component structure of impulsivity, by Principal Components Analysis of 12 subscales, from four widely used self-report measures of impulsivity. Two hundred and forty five subjects from the UK general population completed the Eysenck Impulsiveness Scale (Eysenck, Pearson, Easting, & Allsopp, 1985), the Dickman Impulsiveness Scale (Dickman, 1990), Barratt's Impulsiveness Scale (Patton, Stanford, & Barratt, 1995) and the BIS/BAS scales (Carver & White, 1994). Analysis of the subscales provided evidence in support of a three-component structure of impulsivity. Components were labelled Non-Planning Dysfunctional, Functional Venturesomeness and Drive/Reward Responsiveness.

مقدمه انگلیسی

Various operational definitions of impulsivity have been proposed, each highly dependent on theoretical presuppositions (Pulkinnen, 1986). Studies have highlighted the lack of consensus about the theoretical underpinnings of impulsivity, the number of, and content of dimensions that constitute the construct (Gerbing, Ahadi, & Patton, 1987; Parker, Bagby, & Webster, 1993).
Given these differences in both terminology and theory, it is unclear whether various measures which aim to operationalise models of impulsivity are empirically distinct, or whether they are in fact highly related measures tapping the same construct. In order to investigate this issue, the aim of the present study is to analyse the component structure of four widely used self-report measures of impulsivity; the Dickman Impulsivity Inventory (DII), the Eysenck Impulsiveness Questionnaire (I7), the Barratt Impulsiveness Scale (BIS-11) and Carver and White's BIS/BAS scales.
Examination of various definitions of impulsivity highlight the difficulties faced when attempting to measure the construct. Some definitions describe the relationship between inadequate thought and future actions, such as that of Dickman, who defines impulsivity as the tendency to deliberate less than most people of equal ability before taking action (Dickman, 1990). Other definitions may incorporate the concept of risk taking behaviour, as does Eysenck, for whom impulsivity is a characteristic of people who act on the spur of the moment without being aware of any risk involved (Eysenck & Eysenck, 1985; Eysenck, Easting, & Pearson, 1984). Coles (1997) describes impulsivity at a multi-faceted level, as involving an impulse, the behavioural expression of that impulse, and the situation in which both occur.
A number of studies have investigated the structure of the impulsivity construct. Gerbing et al. (1987) identified three broad dimensions among self-report scales and behavioural measures of impulsivity. The first of these encapsulates a tendency to engage in spontaneous thoughts/behaviours, which could be otherwise labelled as restlessness or distractibility. A second broad dimension included in the measures was a tendency to be disorganised and unprepared in everyday activities. Thirdly, a group of items were identified which could be labelled as having carefree or happy-go-lucky attitudes and behaviours.
Parker et al. (1993) describe a Principal Components Analysis of the impulsivity subscales of three widely used personality measures. The study revealed that the subscales of the Multi-Dimensional Personality Questionnaire (MPQ; Tellegen, 1982) and the Guilford–Zimmerman Temperament Scale (GZTS; Guilford, Zimmerman, & Guilford, 1976), which were both developed as unidimensional scales, were in fact comprised of two similar structures, a cautious and a spontaneous factor, suggesting impulsivity could best be explained by a two-component model.
This and other studies (White et al., 1994) suggest that impulsivity can be viewed as having multiple dimensions, rather than being measured as a unidimensional construct. Based on these findings, researchers and clinicians choosing a self-report measure of impulsivity should take care to ensure that the measure does assess multiple components of impulsivity, rather than a single or narrow component.
It is hardly surprising that attempts to inter-correlate self-report measures of impulsivity have resulted in inconsistent findings. Whereas several studies have reported no statistically significant correlations (Gerbing et al., 1987; Luengo, Carrillo-de-la-Peña, & Otero, 1991), others have described positive correlations between measures (Dickman, 1990; O'Boyle & Barratt, 1993, Parker & Bagby, 1997).
Of the most widely used self-report measures of impulsivity, the oldest is that devised by Barratt (1959), who was interested in the relationship between anxiety and impulsiveness. In this conceptualisation, impulsiveness is defined as a first order personality trait, closely linked to Eysenck's extraversion, sensation seeking and hypomania (Barratt & Patton, 1983). Barratt's original impulsivity measure was constructed to measure impulsivity as a unidimensional personality trait, but was later amended to incorporate six then three dimensions, the first multi-dimensional measure of impulsivity (Barratt, 1972; Barratt, 1985; Barratt & Stanford, 1995). The current Barratt scale, BIS-11 (Patton et al., 1995) proposes that impulsivity is made up of three broad dimensions: motor, non-planning and cognitive impulsiveness.
A second well-validated and widely used measure of impulsivity is Eysenck's Impulsiveness Scale (I7: Eysenck et al., 1985). Eysenck and Eysenck (1977) originally postulated that impulsivity was constructed of four main dimensions: narrow impulsiveness, risk taking, non-planning and liveliness. Following this, a Principal Components Analysis of impulsivity and sensation seeking scales suggested that there were only two components of impulsivity: Impulsiveness and Venturesomeness (Eysenck & Eysenck, 1978; Eysenck & Zuckerman, 1978). The current Impulsiveness Scale (I7) contains three unidimensional subscales: Impulsiveness, Venturesomeness and an Empathy scale. These scales are closely correlated with Eysenck's Psychoticism, Extraversion and Neuroticism, respectively (Eysenck & Eysenck, 1978).
A third measure is the Dickman Impulsiveness Scale (DII; Dickman, 1990). Dickman, 1985 and Dickman, 1990 recognised that the consequences of impulsivity on cognitive functioning need not always be negative, and therefore proposed the two dimensions of dysfunctional and functional impulsivity. Dysfunctional impulsivity is the tendency to act with less forethought than most people of equal ability when this tendency is a source of difficulty. Conversely, functional impulsivity is the tendency to act with relatively little forethought when such a style is optimal.
A fourth measure is the BIS/BAS scales, developed by Carver and White (1994) to provide a self-report measure of Gray, 1972 and Gray, 1981. Gray proposed a neuropsychological theory, which identifies two dimensions of personality; Impulsivity and anxiety. It is postulated that two mechanisms exist that explain individual differences in the two personality dimensions, and these are the appetitive behavioural approach system (BAS), associated with the trait of impulsivity, and an avoidant behavioural inhibition system (BIS) which controls anxiety.
The BAS consists of three unidimensional subscales: Fun seeking, Reward Responsiveness and Drive, along with the single BIS subscale, thereby suggesting a 4-factor structure of impulsivity (Carver & White, 1994). Attempts to replicate this factor analytic study have supported a 4-factor structure and the two distinct BIS/BAS scales, but suggested that the model of fit is not highly significant (Heubeck, Wilkinson, & Cologon, 1998; Jorm et al., 1999). Studies have also questioned the validity of the Reward Responsiveness scale due to its low loadings in addition to it's loading onto both the BAS and BIS scales (Jorm et al., 1999; Ross, Millis, Bonebright, & Bailley, 2002).